The air bag unit, provided on a fixed portion of car body in front of the seat in a vehicle, plays an important role for protecting the passengers in the vehicle from injury due to collision against the car body. The air bag is inflated instantaneously by pressure of a reaction gas released a) from an inflator fixed on the steering wheel for a driver or b) from an inflator fixed on an instrument panel or other fixed portions of a car body for a passenger in case of an emergency such as the collision of the vehicle.
In an air bag unit for a passenger in the assistant seat, as shown in FIG. 6, the gas generating agent in the inflator 2 induces a chemical reaction by a collision signal from a collision detecting sensor (not shown) when the deceleration of the vehicle exceeds a certain level. The air bag 3 is instantaneously inflated and expanded by the generated reaction gas. Then, the air bag 3 receives the person M, who is thrown forward by inertia and protects the person M from collision against the car body.
A large space is present between the assistant seat and instrument panel or front windshield. Moreover, such a large space is often asymmetrical from the left and right of the car body, and such an asymmetrical shape differs widely according to each car model. In this respect, the conventional type air bag 3 for a passenger is formed in a complicated shape as shown in FIG. 7 in order to effectively protect the passenger by properly fitting the shape of such a large space.
When the air bag 3 takes such a complicated shape, the sewn shape when base cloths 3a and 3b are sewn up becomes also complicated as shown in FIG. 7, and it is not possible to automatically sew up the air bag 3 by machine. As a result, the conventional type air bag 3 for a passenger is manually sewn.
The same problem exists with the air bags for the passengers in the back seats, although these are not shown in the figures.
Manual sewing of these base cloths 3a and 3b results in intricate sewing for the air bag 3, and a lot of time is required for producing the air bag 3. Because the base cloths of complicated shape are sewn up, the convention type air bag for passengers does not flexibly fit a wide variety of asymmetrical shapes, which differ according to each car model. As the result, there have been problems with the conventional type of air bag for passengers, such as low productivity or high manufacturing cost.